/* Copyright 2022 The OpenXLA Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
==============================================================================*/

#ifndef XLA_SERVICE_SPMD_COLLECTIVE_PERMUTE_MOTION_H_
#define XLA_SERVICE_SPMD_COLLECTIVE_PERMUTE_MOTION_H_

#include "absl/container/flat_hash_set.h"
#include "absl/status/statusor.h"
#include "absl/strings/string_view.h"
#include "xla/hlo/ir/hlo_module.h"
#include "xla/hlo/pass/hlo_pass_interface.h"

namespace xla {

// This pass moves collective permutes at the end of a loop to the beginning,
// which makes overlapping possible for megascale decomposed ops.
class CollectivePermuteMotion : public HloModulePass {
 public:
  CollectivePermuteMotion() = default;
  absl::string_view name() const override {
    return "collective-permute-motion";
  }

 protected:
  absl::StatusOr<bool> RunImpl(
      HloModule* module,
      const absl::flat_hash_set<absl::string_view>& execution_threads) override;
};

}  // namespace xla

#endif  // XLA_SERVICE_SPMD_COLLECTIVE_PERMUTE_MOTION_H_
